Conversion of ortho tertiary alkyl phenols to para tertiary alkyl phenols



May 22, 1951 P. M. ARNOLD Y CONVERSION OF ORTHO TERTIARY ALKYL PHENOLS TO PARA TERTIARY ALKYL PHENOLS Filed Aug. 5, 1947 ATTORNEYS Patented May 22, 1951 VUNITED y STATES rN-r orifice Philip M. Arnold, Bartlesville, Qkla assigner t9 V.Ifhilips lPetroleum ICompany, a ^`corporation,.of

Delaware Application August V, 1947, KSerial N o. 766,437

14 Claims. (ol. ,25o- 624) v This invention relates to the isomerization .of ortho tertiary alkyl `phenols `to the corresponding para tertiary alkyl phenols. In one :preferred embodiment the invention relates to such iso.- merization as effected on the tertiary butyl com.- 'pounds The invention provides an improved chemical method for converting the `ortho to the para compounds.

The various Atertiary alkyl lphenols are important chemicals commercially. Certain of these compounds are applied per se to different uses while others .are more important as chemical intermediates. In many instances the para com- Y pounds are found -to be more lvaluable than the orthocompounds. Accordingly, various processes have been proposed lfor isomerizing ortho tertiary alkyl fphenols to para tertiary alkyl phenols. These processes have suffered from variou disadvantages, among which may be included substantial losses of material in the form of high,- boiling residue. This result may be explained perhaps by the long digesting time normallyfrequired to effect the attainment of an equilibrium isomerization.

Para tertiary 4butyl-phenol is of particular `interest at the present time and `is Vprepared vcommercially `by alkylation of phenol With isobuty-lene. Alternatively, rit may be preparedbyalkylation of phenol'Withtertiary'butyl alcohol, or with tertiary -butyl chloride. Numerous catalysts may be employed for the alkylation reaction, and ordiriarily the catalyst 'is -of an acidic nature. As s pecicexamplesmay be 4mentioned sulfuric acid, aluminumchloride, various other .Friedel-Crafts type metal halides, '.hydrouoric acid, hydrochloric acid, phosphoric acid, toluene -sulfonic acid, and the like. The alkylation may also be accomplished in the presence of natural clays, preferably those which have been acid treated. Recently the use of a synthetic silica gel catalyst activated with minor'proportions of alumina or other metal oxide has been described my Schulze and Mahan in patent application Serial No.` 653,590 led March 1l, 1946. Regardless-of .the catalyst used .and the yreaction .conditions .employed, substantial amounts of the ortho isomer are formed, Withconsequent reduction in lyield ofthe desired para isomer.

It islanlobject of this .invention to isomerizeV ortho tertiary alkyl phenol to para tertiaryalkyl phenol.

'.-It is lanother object of the vinvention toaccom.- plish such an isomerization with extremelyhigh ultimate yields 1 of Ythe desired para isomer.

butyl phenol by means of 4a series .of chemical reactions into para tertiary butyl phenol.

Yet another .object isfto ,oom-ort Yortho .tertiary amyl phenol into para tertiary .amyl phenol.Y

Further objects and advantages of ,the invern.- tiori will abe kapparent :to .Skilled in .tile art from the .accompanying .disclosure ariddisoll. ion.`

-In .aeeordanee with .a preferred embodiment .of my .ortho :tertiary .butyl phenol from any source is irst subjected to .en .alleviation rer action .with .isohutyleliein .ordorcto form .ditertiary butyl phenol. Whilelisobntvlene is tile preferred alleviating reaetant, tsloatvl .chloride or t-.loiltyl alcohol may be .employed .if .desired .in .Conjunctonwithsuitable.catalysts The resulting .eli-alleviated Qomnound is ,almost wholly ZA-.ditertiary fhutyl phenollllie res. ing :alleviation .mixture :iS -Sllbieoted to suitable separation .steps .to .recover (the diebutyl .comey poundasan intermediate product.

The thus-recovered cli-.tertiary butyl phenol :is

next subjected .to a dealkylation reaction, `'in thecovered as the .para compound. Of course, 4iso-` butvleneie a proxiiiotof theoeallrvletioo reefohoa and. this .materielle.reooreredeoolrooyoleri .to ille alleviation reactionln this meneer or internelly feolrlrzlete .ostello orooess yis provided. ,and when .the various steps are carriedlout yunder the preferred .reaetionoondltoes .and .inthe preeerloe of the preferred ,catalysts kof the invention, yery little meteor fisobutrlene'lreeoterit :is required and o `large production -of pero tertiary' bolliti phenol is r..eo.l.ize fll Likewise.' ythe .loss Aof .ortho tertiary ,butyl -nlleiiol .Charged .to fthe processie the for-.1n foflheev -alkrllplieriols and tare, ,is-erf irerrloly small '.eevwlll Aloo illustrated ,-bolQW! Tilo invention will be described with particular refer.-

eriee .to :the oorlversioo of' q'ortho ,tertiary lolliyl phenol to the :corr spending-.para tertieryblltsll- Pho1lo1-` iliolvvever. .ltfwill loe .understood lovfthos skilled -zinthe 'tart that similar iprocedures hare' `=.Alfurther'object is to convert ortho .tertiary l55 employedwi-th suitablefmodiicatiomwhere.-nee.-

sary, when other tertiary alklyl phenols are to be treated and produced.

The accompanying drawing illustrates diagrammatically by means of a schematic representation oneV arrangement of apparatus elements and flow of materials therethrough suitable foripracticing a specific and preferred embodiment of my invention. In view of the diagrammatic nature of the drawing it will be appreciated that numerous elements of auxiliary equipment, such as pumps, valves,v heat exchangers, control means, condensers, furnaces, and the like, as well as specic details of construction of the various elements illustrated, are not shown in the drawing-for the sake of simplicity. Inasmuch as such items are well understood by those skilled in the art, they need not be described in further detail here. It will also be appreciated, of course, that various alternative arrangements may be employed without departing from the broad scope of the invention. Figure 1 shows one arrangement of apparatus and flow of materials, while Figure 2 illustrates an alternative arrangement for the latter part of the process.

- In the drawing, a feed stream comprising ortho tertiary butyl phenol from any source (not shown) is introduced via line I into alkylation zone 2. Isobutylene recycled from a subsequent separation step, plus an inert hydrocarbon diluent such as n-hexane, is added to the feed stream from recycle line 4. Make-up isobutylene and/or diluent may be introduced as needed via line 3. The eilluents from alkylation zone 2 pass via line 5 to fractionator 6, in which ditertiary butyl phenols and heavier products are separated from unchanged o-tertiary butyl phenoLn-hexane, and any unreacted isobutylene. The latter materials are taken overhead from fractionator 6 via line 'I, and returned to reactor 2 via line 4, while the dialkyl phenols and higher boiling products pass via line 8 to dealkylation zone 9. A second diluent stream, which may be n-hexane or some other inert hydrocarbon, is recycled to dealkylation zone 9 from fractionator I4 via line I5, make-up diluent being supplied from line 25,. The products of the dealkylation reaction are carried by line I0 to fractionator II,-fr,om which isobutylene is taken as an overhead product ior recycling to reactor I Via lines I 2 and 4, and higher boiling products are passed via line I3 to fractionator I4. 'I'he overhead product from fractionator I4, i e., the hydrocarbon diluent, is recycled to reactor 9 via line I5, while the kettle product of unit I4 is carried via line I5 to ractionator Il. Here is a separation is made between o-tertiary butyl phenol, p-tertiary butyl phenol, and the dialkyl phenols Yand heavier products. The ortho isomer is passed to reactor 2 via lines I8, I2 and 4, and the para compound is removed as the principal product of the process via line I9. The dialkyl phenols and heavier products may be removed from the system via lines 20 and 2I, or may be partly or wholly recycled to dealkylation reactor 9. Vacuum fractionation may be employed advantageously in fractionator Il, because of the'relatively high `boiling points of the alkyl phenols, ora third inert hydrocarbon diluent stream may be employed to facilitate this separation. Y

A modification of the separation steps which may be desirable in certain instances is shown in Figure 2. The eliiuents from dealkylation re actor 9 are passed via line IIJ to fractionator II for recovery of isobutylene as an overhead product through line I2. The remaining material .flows through line I3 into fractionator I4. Fractionator I4 is operated so as to yield an over head product comprising the inert diluent and o-tertiary butyl phenol, and a kettle product comprising p-tertiary butyl phenol andl higher boiling products. The overhead product removed Via line 23 is then fractionated in column 24 to separate the diluent from the o-tertiary butyl phenol, the former being recycled via line I5 to dealkylation reactor 9 and the latter being recycled via line I8 to alkylation reactor 2. The kettle product of column I4 is removed via line I6 and then fractionated in unit Il to produce `the p-tertiary butyl phenol product overhead through line I9 and the dialkyl phenols and higher boiling materials as kettle product which is removed through line v20 either for recycle via line 22 to dealkylation reactor 9 or for removal from the system through line 2 I.

' .The alkylation reaction in unit 2 is effected in the presence of a suitable catalyst, and reaction conditions do not differ greatly from those used in the heretofore-known alkylation of phenol with an olefin to produce a mono-alkyl phenol. In such an alkylation, there is usually formed a small amount of the dialkyl phenol, but it has not been suggested before, so far as I am aware, to subject the mono-alkyl phenol to a further alkylation in order to form the dialkyl phenol deliberately.

Several types of catalyst may be employed to concert o-t-butyl phenol into 2,4-ditertiary butyl phenol by reaction with isobutylene. Aluminum chloride and other metal halide catalysts of the Friedel-Crafts type are suitable, but tend to produce undesirably large amountsof Icy-products such as olen polymers and polyalkyl phenols heavier than the di-alkyl derivative, with consequent low ultimate yield. The situation is similar with the strong acid catalysts, such as sulfuric acid, toluene sulfonic acid, and thelike. Anhydrous hydrogen fluoride is somewhat more selective.

Another group of catalysts comprises those known as contact materials, among which are included bleaching earths, clays, various other naturally occuring silicates, especially when activated by partial drying and/or with acids. Also, activated alumina, bauxite, and the like have some utility. l

It is preferred, however, in the practice of my invention, to alkylate the ortho tertiary alkyl phenol with an isoolefln in the presence of a solid adsorbent catalyst comprising a synthetic precipitated silica gel promoted by impregnation with relatively minor proportions of certain metal oxides such as aluminum oxide, titanium oxide, zirconium oxide, and the like. When these catalysts are employed, reaction conditions may be so selected that the reaction products are almost exclusively the dialkyl phenols, with very little higher boiling material or aralkyl ethers being formed.

The solidladsorbent catalysts which are a feature of the present process are most accurately described as dried gels and are characterized by their chemical composition, their physical properties and by the speciic'methods of preparation, said methods being responsible in large part for their chemical activity. Although these catalysts are broadly referred to as metallic oxide promoted silica gel compositions, it is to be understood that they have distinctly different catalytic properties from .the naturally occurring minerals tion temperature.

Which containsm of thes'a'liie4 components;

Forkexample, the acidztreated bleaching earths, clays,v kaolins and. similar naturally occurring silicates are quite different. in composition fro the preferred synthetic catalysts.

. The catalysts' employed in this invention. are

prepared by forming a hydrous silica gel or jelly usually from` an alkali metal silicate-andan acid, washing soluble material from the gel, treating or Aactivating said gel withv an aqueous solution of a suitable metal salt, 'and subsequently washing andV drying the treated material. manner a part ofthe metal, presumably in the form of a hydrous oxide or loose hydroxide cm` pound formed by hydrolysis, is selectively ad-` sorbed by the hydrous silica and is not removed by subsequent Washing. The most frequently used catalyst of this type is a silica-aluminacatalyst ,prepared by treating awet or partially dried hydrous silica gel With an aluminum saltv solution, such as a` solution of aluminum chloride or sulfate, and nally Washing and drying the treated material.y Other catalysts of a similar nature may be prepared by using, instead of an aluminum salt, a hydrolyzable salt of a metal selected from group III-B or from group IV-A of the periodic system. More particularly, salts of indium and thalliumin addition to aluminum in group III-B `and salts of titanium, zirconium and thorium in group IV-A are employed. 'Whether prepared by this method or by some modication thereof, the catalyst will contain a major portion of silica and a minor portion of metal oxide. This minorportion of metal oxide, such as alumina, will generally not be in excess of l0 per cent by weight and will usually range from about 0.1 to 2.0 per cent by Weight.A

Reaction conditions for the alkylation of the lower temperatures of about atmospheric or r somewhat above atmospheric are usually adequate and in fact necessary to prevent excessive polymerization of the olen and other side reactions. Moderately elevated pressures are preferred and it is usually desirable that the` pressure be sufficiently high to maintain liquid phase or mixed phase conditions at theV particular reactertiary alkyl rphenol over the tertiary olefin reactantis used as -a further means of' obtaining high "ultimate yields through the avoidance of.r

olefin polymerization. An inert hydrocarbon diluent. is` also advantageous, and this may bean aliphatic oralicyclic .hydrocarbon or hydrocarbons. Flow rates of vtotal reactant mixture may range from 1` to 10 liquid volumes per volume of catalyst per hour, ,the exact figure depending upon the catalyst. temperature, and reactants employed.

For the dealkylation. reaction a-nylsuitable catalyst/may be employed by which the '2,4-ditertiary alkylA phenolV is' converted into a YmixtureA of the desired para tertiary alkyl phenol and the corresponding ortho compound. In general, any of the catalysts mentioned above assuitable for In this With less active clay-type A molar excess of the orthothe alkylation may also beemployed in the dealkylaton reaction. Where acid `type catalysts,`

lDealkylation temperatures arergenerally higherA than alkylation temperatures, and in the case ofv silica alumina catalysts will be atleast about 300 F. 'and may'range' as Vhigh as 400 to 500 F. With yless active surface catalysts higher temperatures are required. With acid type catalysts, temperatures of`200600 F. vare suitable. Low,

pressure is required in theA .dealkylation reaction for optimum results. While Ysub-atmospheric pressuresare desirable, they are not necessary and it` is ordinarily preferred from the standpoint of operating convenience to use substan-V tially'atmospheric or slightly superatmospheric pressures,'such as 10 to 20 p. s. i. g. When a paraiiinic or naphthenic diluent is used in the dealkylation reaction, the proportion of same is ordinarily less than that used in the alkylation step. A suitable flow rate may be selected from a wide range of operable values in accordance with the temperature and catalyst used in any given instance.

. The following specic example is given to i1- lustrate one mode and set of conditions suitable for carrying out the process of my invention. It will, vof course, be appreciated that variations may be made Within the broader scope of the invention.

-V'A mixture of o-tertiary butyl phenol, isobutylene, and n-hexane, in a mol ratio of Iazl'zl,`

was charged to a steel reactor containing fresh silica-alumina catalyst at a temperature of 200 F. The catalyst had been prepared by adsorption l of alumina on'a hydrous silica gel from an aqueous solution of aluminum sulfate. A flow rate of approximately 5 liquid volumes of feed per volume of catalyst per hour was maintained, with a pressure of 500 p. s. i. g. in the reaction zone. The `effluents from the reactor were separated by fractional distillation into a recycle stream containing the diluent, a small amount of vunre acted isobutylene, and the unreacted o-tertiary butyl phenol, and a higher boiling product desired dealkylation of diand tritertiary butyl phenols to mono tertiary butyl phenols occurred to the extent of about per cent per pass, with` the para isomer predominating in the products.

`The' dealkylation effluents were separated by a series of fractional distillation steps into (l) isobutylene,-Which was recycled to the alkylation zone,'(2) n-hexane, which was returned 'to' the dealkylation zone, (3) o-tertiary butyl phenol, which was recycled to the alkylation reactor, (4) p-tertiary butyl phenol, the ,desired product,

and (ll unchangedfditertiary'butyl phenols'and` heavier products which were largely returned to.A

the-dealkylation reactor.v Less .than 1 per cent of the o-tertiary butyl phenol charged to the proc.-

ess is lost in the form ofhea'vy .alkyl phenols and tars.

I claim: 1. A process for converting an ortho-tertiary alkyl phenol into the corresponding para. tertiary alkyl phenol isomer, which comprises reacting in a yrst reaction step the ortho tertiary alkyl phenol as the sole phenolic reactant present with a 'compound selected from the group consisting of `olens, alkyl halides, and .alcohols capable of yielding a tertiary alkyl radical which is the same` as" the tertiary alkyl radical of the said ortho compound in the presence of a catalyst for. nuclear alkylation of phenols to form a 2,4-ditertiary alkyl phenol, subjecting said dialkyl phenol in alsecondreaction step to dealkylation in the absence of added phenol and in the presence 'of a phenol dealkylation catalyst to form para .ter-

' 4. A method according to claim 3 4wherein saidY ortho vtertiary butyl phenol is alkylated with isobutylene to form 2,4-ditertiary butyl phenol.

A 5. A method according to claim 4 wherein saidv ortho tertiary butyl phenol is alkylated with isobutylene in the presence ofA a synthetic silicaalumina gel-type catalyst at 200 to 300 F.

6. A method according to claim 5 wherein said alkylation is eiected under sufficient pressurekftoV insure liquid phase operation, and whereinl the resulting 2,4-ditertiary butyl phenol is dealkylated in the presence of a synthetic silica-alumina gel-type catalyst at a higher temperature of 300 to 500? F. and at a'lower pressure than used ,inu said alkylation. Y

7. A method according toclaiml wherein said- 2,4ditertiary alkyl phenol is dealkylated in the presence of a synthetic silica-alumina gel-type catalyst .at 300 to 509 F. and rat a pressure not exceeding pounds per square inch gauge Vto form a mixture of p-t-alkyl phenol and o-talkyl phenol, the latter is recycled to said rst reaction step, and the former is recovered as the net product of the process.

8. A method `according to claim l wherein said alkylating compound is a tertiary olen.-

9. A method of converting an ortho tertiary alkyl phenol into the corresponding para tertiary alkyl phenol isomer in high ultimate yields whichA comprises alkylating .an ortho tertiary alkyl phenol as the sole phenolic reactant present with a tertiary olein having the same number of carbon atoms as the alkyl group of the phenol, in

the presence of an active phenol alkylating catalyst and an inert liquid hydrocarbon diluent while maintaining a molar excess of the ortho tertiary alkyl phenol over the olen, separating the resulting reaction mixture into fractions in" cluding unreacted ortho'tertiary alkyl phenol,`

diluent', and'2,4.ditertiary alkyl phenol product,

recycling said unreacted ortho'tertiary alkyl phe no1 yand .diluentI to .the alkylation reaction, deal.

kylatin'g'said 2,4ditertiary. alkyl -phenol in the absence of phenol'and' in the presence of anV inert hydrocarbon'diluent and an active phenol dealkylation catalyst at a low pressure, separat.

ing the resultingfreaction mixture into fractions including diluent, tertiary olen, ortho tertiary alkyl phenol, unreactedditertiary alkyl phenol, ,and the desired para tertiaryv alkyl phenol product, and recycling said diluent and unreacted ditertiary alkyl phenolto said dealkylation reac tion and said tertiary `olefin and ortho tertiary alkyl phenol to said alkylation reaction.

10. A method accordingto claim 9 wherein ortho Vtertiary butyl phenolis converted into paratertiary butylphenol.

11. A method according to claim 9 wherein .Y ortho tertiary amyl phenol is converted into para tertiary amyl phenol.

12. A method according to claim 9 wherein the alkylation reaction mixture is separated by frac' tional distillation into one fraction comprising unreacted ortho tertiary alkyl phenol and diluent and another higher boiling fraction comprising a- 2,4-ditertiary alkyl phenol.

l 13.-.A method according to claim 9 wherein the.4 dealkylation reaction mixture is Yseparated byfractional distillation into a fraction comprising tertiary olefin, `another fraction comprising dilu.` ent, another fraction comprising ortho tertiary alkyl phenol, another fraction comprising para tertiary alkyl phenol product, and another frac-v tion comprising unreacted ditertiary alkyl phenol plus heavier products, each of said fractions being higher boiling than the preceding named fraction, and wherein Ya portion of said lastnamed fraction is recycled to the dealkylation reaction while'another portion is removed from` the system.

14. A method according to claim 9 wherein thel dealkylation reaction mixture is separated by fractional distillation first into a low-boiling fraction comprising tertiary olen, `and a higherboiling fraction, said higher boiling fraction is separated into a low-boiling fraction comprising diluent and ortho tertiary alkyl phenol and a higher-boiling fraction comprising para tertiary alkyl phenol product and heavier alkyl phenols, and each of said two latter fractions is separated;

into its constituents. PHILIP M. ARNOLD.

REFERENCES CITED The following references are of record in the le of this patent:

Y UNITED STATESV PATENTS Number Oblad Feb. 24, 

1. A PROCESS FOR CONVERTING AN ORTHO TERTIARY ALKYL PHENOL INTO THE CORRESPONDING PARA TERTIARY ALKYL PHENOL ISOMER, WHICH COMPRISES REACTING IN A FIRST REACTION STEP THE ORTHO TERTIARY ALKYL PHENOL AS THE SOLE PHENOLIC REACTANT PRESENT WITH A COMPOUND SELECTED FROM THE GROUP CONSISTING OF OLEFINS, ALKYL HALIDES, AND ALCOHOLS CAPABLE OF YIELDING A TERTIARY ALKYL RADICAL WHICH IS THE SAME AS THE TERTIARY ALKYL RADICAL OF THE SAID ORTHO COMPOUND IN THE PRESENCE OF A CATALYST FOR NUCLEAR ALKYLATION OF PHENOLS TO FORM A 2,4-DITERTIARY ALKYL PHENOL, SUBJECTING SAID DIALKYL PHENOL IN A SECOND REACTION STEP TO DEALKYLATION IN THE ABSENCE OF ADDED PHENOL AND IN THE PRESENCE OF A PHENOL DEALKYLATION CATALYST TO FORM PARA TERTIARY ALKYL PHENOL AND ORTHO TERTIARY ALKYL PHENOL, RECYCLING THE LATTER TO SAID FIRST REACTION STEP, AND RECOVERING SAID PARA TERTIARY ALKYL PHENOL FROM EFFLUENTS OF SAID SECOND REACTION STEP AS THE NET PRODUCT OF THE PROCESS. 